In construction or repair, not a single object is complete without laying or replacing electrical networks. And of course, the brand of the cable is of decisive importance. Cable products for internal wiring must not only meet the requirements for maximum current, insulation, allowable heating, but also fire safety requirements.
NYM cable design
The most popular cable product in recent times is the NYM cable. Description and characteristics are given below. It consists of single or multi-wire copper current-carrying conductors in insulation made of chalk-filled PVC compound. Color marking of cable cores:
- 2-core - black, blue;
- 3-core - green-yellow, black, blue;
- 4-core - green-yellow, black, blue, brown;
- 5-core - green-yellow, black, blue, brown, black.
The outer shell is made of chalk-filled PVC compound. Sheath color - light gray. The overall shell is filled with extruded chalk-filled rubber.
Marking
The type designation of the cable product consists of the letters NYM, indicating:
- N - standard cable (in German classification);
- Y - PVC insulation (PVC in European interpretation);
- M – the presence of an outer shell.
Additionally, through a hyphen, the symbols J are applied - the presence of a green-yellow wire, or O - a product without a yellow-green core. After that, the number and cross section of the cores, the operating voltage are indicated.
For example, the marking NYM-J 3x2, 5-0, 66 indicates a standard cable with an outer sheath in PVC insulation with three cores with a cross section of 2.5 sq. mm for voltage 0.66 kV.
In the marking of domestic manufacturers that comply with the requirements of GOST R 53769-2010, such a cable will be marked NYM 3x2.5 ok (N, PE). Here “o” is a single-wire core (as an option, “m” is a multi-wire), “k” is a round core, N and PE are zero and protective cores. Often they say not a cable, but a NYM wire. Cable - what is it? The definition given in the state standard reads: "A cable product containing one or more insulated cores enclosed in a sheath." Therefore, it is correct to call NYM not a wire, but a cable.
Main parameters
Specifications are important for both professionals and DIYers:
- Rated voltage is 0.66 kV.
- Operating temperatures - from -50 to +50 0C.
- Minimum gasket temperature - from -5 0C.
- Minimum bending radius - not less than 4 cable diameters.
- Service life - 30 years.
- Number of cores - from 1 to 5.
- Range of core cross-sections – from 1,5 to 35 sq.mm.
- Packing - coils of 25, 50 m or on a drum of 500 m.
And, of course, the most important parameter of a cable is its allowable current. It is determined depending on the cross-section of the cores, the laying method, and the outside temperature. For an approximate estimate, you need to use the tabular data from the PUE:
| section, mm.sq. | current, A |
| 3x1, 5 | 15 |
| 3x2, 5 | 21 |
| 3x4 | 27 |
| 3х6 | 34 |
| 3x10 | 50 |
It should be noted that the cable can be produced according to European standards (German), GOST, or TU (technical specifications). The latter are developed by the manufacturer. Therefore, cable parameters, such as insulation thickness, core cross-section tolerance, may vary between different NYM manufacturers. Cable reviews, depending on the manufacturer, receive both positive and not so.
Advantages and disadvantages
Like any product, the NYM cable also has its own chips. Its features are described below:
- High quality insulation material. PVC compound is heat-resistant, does not support combustion, and is flexible enough.
- Ease of installation. Due to the soft filler, the outer protective cover can be easily removed without the risk of damage to the insulation of current-carrying conductors.
- Quality conductive conductors made of soft copper wire. Easy to twist for a quality connection.
- The light gray color of the outer shell is very convenient for marking with a ballpoint pen or marker during installation.
- Long service life, standard 30 years.
- The cable is not recommended for outdoor installation, it is not resistant to direct sunlight.
- Mismatch of the cross-section of the cores indicated in the marking. You often hear “I bought a NYM cable, what is this nonsense?” And everything is very simple: now the production of products under this brand has been mastered both at domestic cable plants and in neighboring countries. And not all of them comply with German standards or even our GOSTs.
Application
NYM is a cable whose description indicates that it is intended for single fixed laying indoors only. Laying in a bundle without additional protection is not allowed. It is also not allowed to use a cable of this brand for direct connection of electrical appliances, in extension cords. Laying methods are regulated by the manufacturer's recommendations and regulatory documents on electrical and fire safety. The cable allows laying in cavities and channels of wall panels, in wall strobes in a layer of plaster, in electrical pipes and ducts. There is an opinion that NYM cables are allowed to be laid openly on wooden walls, but this is not so. The electrical installation rules clearly indicate the possibility of open laying only in pipes or boxes, and hidden inside wooden walls - in metal pipes of any wire, including NYM. Cable, photowhich is posted below is mounted correctly.
Cable Selection
On the domestic market, there are mainly cable products of domestic production or an "unnamed" factory. When choosing, pay attention to the marking, any serious cable plant always puts its logo or name. This is at least minimal, but still a guarantee of quality.
- Sometimes sellers recommend using SHVVP, PVA instead of NYM. Do not fall for this trick: SHVVP and PVA are cords, and NYM is a cable. The description regulates completely different areas of their application. Cords - for connecting household electrical appliances and extension cords, cable - for fixed wiring.
- Use cables with a third green-yellow core for protective earthing.
- When choosing a cable section, you can be guided by a simple recommendation: for lighting - 1.5 sq. mm, for a socket network - 2.5 sq. mm, for an electric stove with an oven - 4-6 sq. mm.
- If in doubt about the quality of the cable, buy a small piece, 1 meter is enough. Check the cable for flammability - the insulation should not support spontaneous combustion.
- It is also advisable to check the cross section of the wires. If you don't have a micrometer, you can simply wrap 10 turns of bare wire tightly around a pencil. And then measure the winding length with a regular ruler. Dividing it by 10 gives the actual diameter of the wire.
